Cancer Enabling Inflammation

Slide 1 · Cancer-Enabling Inflammation

How inflammatory and stromal cells support malignant progression

Tumor microenvironment • mechanisms • clinical interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Identify the cellular participants in tumor-associated inflammation.

Explain six proposed mechanisms that enable cancer hallmarks.

Differentiate protumor inflammation from effective antitumor immunity.

Interpret macrophage polarization and therapeutic implications critically.

Slide 3 · Inflammation is an enabling characteristic

Cancer-promoting inflammation facilitates acquisition or expression of other hallmarks.

It is an enabling condition, not a synonymous label for malignancy.

Its effects arise through tumor–host interactions.

Inflammatory microenvironment

Support for hallmark functions

Tumor progression

Slide 4 · A paradox: Abundant inflammation, ineffective restraint

Infiltrating cancers frequently provoke chronic inflammatory reactions.

The reaction can coexist with continued malignant expansion.

Cellular presence does not establish successful tumor-cell killing.

Inflammatory infiltrate

Weak net tumor control

Progression continues

Slide 5 · “Wounds that do not heal”

The textbook uses a persistent-wound analogy for infiltrating cancers.

Inflammatory and repair programs may remain active around the tumor.

Unlike successful repair, the malignant stimulus persists.

Persistent tumor

Chronic inflammation / repair

Remodeled tumor habitat

Slide 6 · Causal interpretation requires restraint

Experimental support

Tumor–stroma cross-talk

Causal pathways in models

Clinical interpretation

Human tumor heterogeneity

Do not infer individual prognosis

Multiple cancer-enabling effects as proposed mechanisms.

Much supporting mechanistic evidence comes from animal models.

The contribution of each pathway varies with cellular context.

Slide 7 · The tumor microenvironment is multicellular

Tumor cells coexist with infiltrating leukocytes and resident stromal cells.

Fibroblasts and endothelial cells are active signaling partners.

Extracellular matrix (ECM) is both scaffold and source of signals.

Tumor microenvironment

Leukocytes

Fibroblasts

Endothelium

ECM

Slide 8 · Bidirectional tumor–stroma communication

Cancer cells provoke a chronic local inflammatory reaction.

Inflammatory/stromal cells release mediators and remodel the ECM.

The resulting tissue environment feeds back on tumor behavior.

Tumor stimulus

Inflammatory/stromal response

Tumor-supportive milieu

Slide 9 · Local versus systemic effects

Local tissue

Proliferation and invasion

Angiogenesis and immune escape

Systemic illness

Anemia

Fatigue and cachexia

Locally, growth, invasion, blood vessels, and immune function can change.

In advanced cancer, inflammation may produce systemic manifestations.

These are distinct outcomes of a related inflammatory process.

Slide 10 · Systemic manifestations of advanced cancer

Inflammation in advanced disease may contribute to anemia.

Fatigue and cachexia may accompany the systemic reaction.

These symptoms do not measure the success of antitumor immunity.

Advanced cancer

Systemic inflammation

Anemia • fatigue • cachexia

Slide 11 · Six tumor-enabling outputs

Cancer-enabling output

Principal source-described mechanism

More proliferation

EGF; ECM-liberated growth factors

Fewer growth restraints

Proteolysis of adhesion interfaces

Improved survival

Macrophage contact; stromal survival signals

More blood vessels

Inflammatory VEGF

Invasion / migration

ECM remodeling; TNF/EGF; TGF-β

Immune escape

Tregs, CD8 suppression, macrophage PD-L1

Slide 12 · Inflammatory cells supply growth factors

Infiltrating leukocytes can secrete growth-promoting mediators.

EGF is the named example in the cancer-inflammation section.

This is a paracrine route to growth support.

Leukocyte

EGF in local environment

Tumor-cell proliferation

Slide 13 · Activated stromal cells contribute to proliferation

Activated stromal cells are additional producers of growth factors.

The malignant clone is therefore not the only source of proliferative signals.

The influence depends on proximity and responsiveness.

Activated stroma

Growth factor release

Tumor-cell response

Slide 14 · Paracrine support does not require a new driver mutation

Tumor-intrinsic

Altered signaling inside cancer cell

Oncogene-related growth

Microenvironmental

Signal supplied by host cells

EGF and related factors

A growth-promoting signal may originate outside the malignant cell.

This differs conceptually from oncogene-driven constitutive growth.

Environmental inputs can cooperate with tumor-intrinsic alterations.

Slide 15 · The extracellular matrix stores biologic signals

The ECM provides structural support and binds molecules in tissue.

Proteolysis can liberate growth factors from the matrix.

Matrix remodeling may therefore change both architecture and signaling.

Growth factors associated with ECM

Inflammatory proteases

Released growth signal

Slide 16 · Proteases amplify growth indirectly

Inflammatory-cell proteases act on the extracellular environment.

Liberated ECM-associated factors can augment proliferation.

The enzyme need not be a direct mitogen to support growth.

Protease secretion

ECM factor release

Proliferative stimulation

Slide 17 · Two routes converge on proliferation

Direct

Leukocyte / stromal factor

EGF → tumor cell

Indirect

Protease acts on ECM

Factor release → tumor cell

Direct route: Cells secrete growth factors such as EGF.

Indirect route: Proteases release matrix-associated growth factors.

Both modify external signals available to cancer cells.

Slide 18 · Growth-support mechanism: Apply the distinction

An inflammatory infiltrate expresses a growth factor: Direct paracrine support.

Protease-rich stroma releases matrix-bound factors: Indirect support.

Neither observation alone proves that inflammation initiated the cancer.

Observe mediator origin

Identify route of action

State supported inference

Slide 19 · Normal epithelia receive growth-inhibitory cues

Interactions between adjacent epithelial cells help restrain expansion.

Epithelial attachment to the ECM also helps regulate growth.

These structural interactions participate in tissue homeostasis.

Cell–cell and cell–ECM contacts

Growth-restraint signals

Controlled epithelial growth

Slide 20 · Cell–cell adhesion is a regulatory interface

Adhesion molecules connect neighboring epithelial cells.

Their function extends beyond simply holding tissue together.

Proteolytic disruption can remove a normal growth barrier.

Intact adhesive interfaces

Protease-mediated degradation

Loss of restraining contact

Slide 21 · Cell–ECM adhesion also restrains proliferation

Attachment to ECM contributes to epithelial organization.

Inflammatory proteases can disrupt molecules mediating this attachment.

Disruption may favor abnormal expansion.

Normal epithelial anchorage

Adhesion-interface degradation

Less external growth restraint

Slide 22 · Proteolysis can remove growth suppressors

Leukocyte-derived proteases degrade adhesion molecules.

The consequence is loss of suppressive cell–cell and cell–ECM cues.

This is environmental disinhibition rather than gene deletion.

Inflammatory proteases

Adhesion degradation

Growth restraint reduced

Slide 23 · Growth suppression: Gene versus tissue context

Intrinsic control

Genetic alteration in cell

Defective checkpoint/signaling

Extrinsic control

Proteases in adjacent stroma

Disrupted adhesive restraint

Tumor-suppressor gene defects alter intrinsic regulatory programs.

Microenvironmental proteolysis changes external growth restraints.

Both may support growth, but they are not identical mechanisms.

Slide 24 · The same protease can affect several hallmarks

Adhesion degradation weakens normal growth restraint.

ECM cleavage releases stored growth factors.

Matrix remodeling may also facilitate tumor invasion.

Tumor microenvironment

Growth factor release

Loss of adhesion

ECM remodeling

Invasion interface

Slide 25 · Structural integrity versus invasive remodeling

Organized tissue

Basement membrane intact

Adhesion constraints maintained

Remodeled tissue

Proteolytic activity

Altered signaling and barrier function

Organized epithelia preserve boundaries and cell contacts.

Protease-active stroma disrupts parts of the matrix environment.

The functional consequence depends on what is degraded and where.

Slide 26 · Anoikis couples survival to attachment

Anoikis is cell death associated with detachment from basement membrane.

Loss of cell–cell interactions can also favor anoikis.

This protects against inappropriate survival of displaced epithelial cells.

Detachment / loosened contacts

Anoikis program

Elimination of displaced cell

Slide 27 · Why detachment is a problem for a cancer cell

Invasion requires cells to loosen attachment to neighbors or ECM.

Such detachment would ordinarily expose cells to anoikis.

Survival during this transition requires additional support.

Invasive detachment

Potential anoikis

Selection for survival support

Slide 28 · Tumor-associated macrophages may blunt anoikis

A protective role for tumor-associated macrophages.

Macrophage integrins may mediate physical contact with cancer cells.

The suggested result is improved survival despite disrupted anchorage.

Macrophage integrins

Contact with tumor cell

Reduced anoikis (proposed)

Slide 29 · Macrophage contact is a physical signal

The proposed mechanism involves adhesion, not only soluble factors.

Direct tumor–macrophage interaction may substitute for some survival cues.

The source does not define a universal receptor pair on every cancer.

Integrin-associated contact

Tumor–macrophage proximity

Potential survival signaling

Slide 30 · Anoikis protection: Level of confidence

Established

Detachment can induce anoikis

Epithelial cell response

Proposed

Macrophage integrin contact

Tumor-cell rescue

Anoikis after detachment is an established epithelial response.

Specific macrophage-mediated rescue is described as suspected.

A mechanistic hypothesis must be distinguished from confirmed clinical benefit.

Slide 31 · Stromal cells may protect against chemotherapy

Tumor–stroma interactions can increase drug resistance.

The suggested mechanism is activation of survival pathways.

DNA-damage stress is the example emphasized.

Chemotherapy-related stress

Stromal survival signaling

Tumor-cell persistence

Slide 32 · Microenvironmental survival is not necessarily genetic resistance

Cancer cell–intrinsic

Mutation or altered cell program

Cell autonomous

Microenvironmental

Stromal survival cues

Context dependent

Stromal protection can alter response without a new resistance mutation.

Intrinsic tumor-genome changes are a separate source of resistance.

A drug-response phenotype can therefore reflect both cell and context.

Slide 33 · Two survival routes should not be conflated

Loss of anchorage

Integrin-related macrophage contact

Anoikis resistance (proposed)

DNA damage / drug stress

Stromal survival pathways

Treatment resistance

Cell contact is proposed to protect against anoikis.

Stromal signaling can buffer cytotoxic stress.

Both enhance survival, but operate in different circumstances.

Slide 34 · Survival question: Disrupted basement membrane

Detachment from ECM

Expected: Anoikis

Proposed: Macrophage contact

Discuss the mechanistic inference and what remains unproved.

Slide 35 · Angiogenesis supplies an expanding tumor

Angiogenesis forms new vessels from pre-existing vasculature.

Tumor expansion can exceed the support of the initial blood supply.

Inflammatory cells can contribute proangiogenic signals.

Growing tumor demand

Proangiogenic signals

New vessel formation

Slide 36 · Inflammatory cells release VEGF

VEGF is an explicit proangiogenic example in the source.

It can act on vascular endothelial cells in the local environment.

This links leukocyte activity to a nonimmune hallmark.

Inflammatory infiltrate

VEGF

Endothelial angiogenic response

Slide 37 · Endothelial cells are active stromal participants

Endothelial cells are named partners in tumor microenvironment cross-talk.

Their response to angiogenic mediators changes tissue vascularity.

The effect is biologically distinct from direct stimulation of cancer-cell division.

VEGF-rich tumor stroma

Endothelial response

Vessel development

Slide 38 · Sprouting angiogenesis: Repair context

In tissue repair, new vessels can sprout from existing vessels.

Endothelial migration and proliferation precede tube remodeling.

Robbins Chapter 3 supplies this normal-process framework.

Vessel sprout

Endothelial migration / growth

Capillary remodeling

Slide 39 · Angiogenesis can be a malignancy-enabling output

The inflammatory cell need not itself form a vessel.

Its secreted mediator can recruit a vascular response.

Stromal reprogramming indirectly assists tumor progression.

Leukocyte mediator

Vascular change

Tumor-supportive niche

Slide 40 · Inflammatory infiltration does not imply antitumor control

Potential host defense

Recognition and cytotoxicity

Effective tumor elimination

Cancer-enabling effect

VEGF and stromal remodeling

Expansion support

A tumor may contain many inflammatory cells and still progress.

Some of those cells can release angiogenic growth factors.

The nature of the infiltrate matters more than its mere presence.

Slide 41 · Invasion requires crossing tissue boundaries

Carcinoma cells must breach basement membrane and interstitial ECM.

Cell attachment, matrix remodeling, and motility participate.

Host inflammatory cells can cooperate in these steps.

Epithelial tumor compartment

Basement membrane / ECM

Invasive movement

Slide 42 · Macrophage proteases remodel ECM

Tumor-associated macrophages can release matrix-degrading proteases.

Remodeling changes resistance of tissues to tumor-cell movement.

This supports a permissive environment for invasion.

Macrophage proteases

Remodeled extracellular matrix

Facilitated tissue invasion

Slide 43 · ECM degradation can support invasion by two routes

Structural

Matrix / adhesion cleavage

Barrier altered

Biochemical

Liberation of bound factors

Cell behavior modified

Proteolysis can physically modify the matrix barrier.

Degradation can also release mediators associated with ECM.

Thus structural and signaling consequences may coexist.

Slide 44 · TNF and EGF may stimulate motility

TNF and EGF are cited as possible motility-promoting factors.

Their actions are conceptually distinct from matrix degradation.

Both cell movement and tissue access are required for invasion.

TNF / EGF in stroma

Tumor-cell motility

Invasive movement (proposed)

Slide 45 · TGF-β may favor epithelial–mesenchymal transition

Stromal TGF-β is described as a potential EMT-promoting factor.

EMT refers to acquisition of a more migratory cellular program.

The source frames its contribution to invasion/metastasis as believed, not universal.

Stromal TGF-β

EMT-associated changes

Motility / invasion potential

Slide 46 · EMT changes epithelial cell phenotype

EMT with reduced epithelial markers such as E-cadherin.

Mesenchymal-associated markers may increase.

These changes are proposed to favor a promigratory phenotype.

Epithelial adhesion program

EMT-associated transition

Promigratory state

Slide 47 · Matrix access and motility are separate requirements

Terrain changes

Macrophage proteases

ECM remodeling

Cell behavior changes

TNF, EGF, TGF-β

Motility / EMT

Proteolysis changes the terrain through which a cell travels.

Motility-inducing factors change the cell’s movement behavior.

Their cooperation gives a coherent mechanistic model of invasion.

Slide 48 · From invasion to metastasis: Do not overstate

Invasion is part of the metastatic cascade, not identical to successful metastasis.

Movement through ECM is only one of several necessary steps.

The source describes inflammation as contributing, not guaranteeing dissemination.

Local invasion

Additional dissemination steps

Possible distant colonization

Slide 49 · Applied mechanism: Macrophage-rich invasive front

Macrophage-rich tumor margin

Predicted: ECM remodeling

Not proved: Distant metastasis

Discuss the mechanistic inference and what remains unproved.

Slide 50 · Antitumor immunity and inflammation are not synonymous

Immune control

Antigen recognition

CD8+ cytotoxicity

Immune escape

Suppressive mediator networks

Reduced CD8+ function

CD8+ cytotoxic T lymphocytes can eliminate antigen-bearing tumor cells.

Other immune populations can instead support a suppressive microenvironment.

An infiltrate contains functionally diverse cells.

Slide 51 · TGF-β is implicated in immunosuppression

Tumor-associated stromal cells can release immunomodulatory mediators.

TGF-β is one named example.

Such signals may contribute to Treg enrichment or cytotoxic T-cell suppression.

Stromal TGF-β

Suppressive immune milieu

Reduced antitumor function

Slide 52 · Regulatory T-cell enrichment can impair tumor control

Stromal mediators may favor recruitment of regulatory T cells (Tregs).

Tregs are an immunosuppressive component of the tumor milieu.

Recruitment shifts the balance away from effective cytotoxicity.

Suppressive mediators

Treg recruitment

Reduced effective immune attack

Slide 53 · CD8+ T cells can be present yet functionally restrained

CD8+ T cells mediate a major arm of tumor cell killing.

Locally produced factors may suppress their function.

Functional state, not only cell count, influences immune surveillance.

CD8+ T cell present

Suppressive microenvironment

Attenuated killing

Slide 54 · Macrophages are not one uniform population

Classical / M1-like

IFN-γ or microbial stimuli

Microbicidal/inflammatory functions

Alternative / M2-like

IL-4 and IL-13

Repair and remodeling functions

Classical (M1) and alternative (M2) activation.

Their programs emphasize different functions.

The categories are endpoints of a spectrum, not perfectly exclusive subsets.

Slide 55 · IL-4 and IL-13 promote alternative activation

IL-4 and IL-13 are named drivers of the M2-like program.

Alternative activation generally supports tissue repair.

Tumor-associated M2-like cells can co-opt these physiologic repair functions.

IL-4 / IL-13

Alternative macrophage activation

Repair-associated program

Slide 56 · M2-like macrophages can build fibrotic stroma

Cytokines that stimulate fibroblast proliferation.

Collagen deposition can follow a repair-associated response.

These changes are frequently present in invasive tumors.

M2-like macrophage factors

Fibroblast proliferation

Collagen deposition

Slide 57 · Alternative macrophage activation can favor angiogenesis

M2-like macrophages can produce proangiogenic cytokines.

Their effects link immune-cell state with vascular remodeling.

The result is a possible protumor support function.

M2-like macrophages

Angiogenic mediators

Vascular support

Slide 58 · Macrophage PD-L1 can suppress effective immunity

The source describes PD-L1 expression on some macrophages.

Checkpoint-ligand signaling can inhibit antitumor T-cell responses.

This is a host-cell contribution to immune evasion.

Macrophage PD-L1

Inhibitory T-cell signaling

Antitumor response reduced

Slide 59 · PD-L1 need not come from the cancer cell

Tumor-cell contribution

Tumor-derived inhibitory factors

Cell autonomous evasion

Stromal contribution

Macrophage PD-L1

Microenvironmental evasion

Tumor cells can employ checkpoint-associated immune escape.

Macrophages in the tumor microenvironment may also express PD-L1.

Cellular source of an immune-regulatory signal matters.

Slide 60 · The M1/M2 binary is a teaching simplification

M1 and M2 represent polar functional states Chapter 3.

Intermediate macrophage programs are common and hard to classify.

Avoid identifying every tumor macrophage as exclusively M2.

M1-like programs

Intermediate states

M2-like programs

Phenotypic continuum — not a time sequence

Slide 61 · Human evidence and model evidence differ

Animal models

Abundant mechanistic observations

Proof-of-principle

Human tumors

Emerging supporting evidence

Context-dependent interpretation

M2-like macrophage enrichment is supported strongly in murine models.

Emerging evidence in human advanced cancers.

Universal clinical prevalence or causal magnitude is not established here.

Slide 62 · Immune evasion is a multicellular output

Suppressive cytokines influence Treg recruitment and CD8+ function.

Macrophage PD-L1 supplies a separate inhibitory mechanism.

Several pathways can converge on reduced tumor-cell elimination.

Tumor microenvironment

TGF-β

Treg recruitment

CD8+ inhibition

Macrophage PD-L1

Slide 63 · One stromal process may affect several hallmarks

M2-like macrophage signals can promote angiogenesis.

Fibroblast proliferation and collagen deposition remodel tissue.

Immunosuppression provides an additional route to tumor persistence.

Tumor microenvironment

Angiogenesis

Fibroblast growth

Collagen deposition

Immune escape

Slide 64 · Cancer-enabling outputs: Integrated mechanism map

Inflammatory/stromal input

Immediate process

Cancer-enabling outcome

EGF and related signals

Growth stimulation

Proliferation

Proteases

Adhesion / ECM remodeling

Growth, invasion

Integrin-linked contact

Proposed anoikis protection

Survival

VEGF

Endothelial response

Angiogenesis

TGF-β / Tregs / PD-L1

Immunoregulatory signaling

Immune evasion

Slide 65 · Inflammation is not a single diagnostic marker

A mixed inflammatory infiltrate does not itself define malignancy.

The source discusses mechanisms, not a diagnostic cell-count cutoff.

Morphology and clinical context remain necessary for interpretation.

Observe infiltrate

Identify participating cells / processes

Interpret in tumor context

Slide 66 · Interpret tumor infiltrates by function

Evidence of function

Mediator / location / cell type

Mechanistic hypothesis

Unsupported shortcut

Infiltrate abundance alone

Prognosis or response claim

Proliferative growth signals and proteases can be growth enabling.

VEGF-rich environments may support vascularization.

T-cell suppression differs from successful antitumor cytotoxicity.

Slide 67 · Therapeutic implication: Modulating inflammation

Interest in interrupting tumor-induced inflammation.

Potential targets include its mediators and downstream consequences.

A plausible target is not automatically a proven anticancer treatment.

Mechanistic understanding

Potential target

Clinical validation required

Slide 68 · COX-2 inhibition: Textbook clinical example

Fewer colonic adenomas with COX-2 inhibition.

Familial adenomatous polyposis (FAP) is its named context.

Do not generalize this example to all cancers or current prescribing policy.

COX-2 inhibition

Fewer colonic adenomas (textbook)

FAP-specific context

Slide 69 · Mechanistic promise and clinical efficacy are distinct

Mechanistic rationale

Known mediators and cell populations

Hypothesis

Clinical efficacy

Patient-level outcomes

Needs direct evidence

Tumor–stroma cross-talk provides biologic treatment hypotheses.

Human outcomes require disease-specific clinical testing.

The full mechanism of tumor manipulation remains elusive.

Slide 70 · Case exercise: Progressive tumor despite inflammation

Inflammatory infiltrate present

Possible proangiogenic / suppressive roles

Tumor still progresses

Discuss the mechanistic inference and what remains unproved.

Slide 71 · Map a mediator to its principal action

Factor / mechanism

Primary interpretation in this lecture

EGF

Proliferation; possible motility

Proteases

ECM factors / adhesion / invasion

VEGF

Endothelial angiogenic response

TNF

Possible tumor-cell motility

TGF-β

Possible EMT; suppressive immune milieu

Macrophage PD-L1

T-cell inhibition

Slide 72 · Five interpretive pitfalls

Do not equate inflammation with effective tumor elimination.

Do not treat every macrophage as M2-like or every T cell as cytotoxic.

Do not equate in vitro/model evidence with routine patient benefit.

Do not infer metastasis solely from protease-associated invasion.

Slide 73 · Teaching synthesis: What inflammation enables

Leukocytes and activated stroma produce signals and remodel tissue.

Growth, survival, vessels, invasion, and immune escape are interconnected outputs.

The net effect is context-dependent; Several proposed pathways remain incompletely resolved.

Inflammatory / stromal activity

Multiple hallmark-enabling routes

Potential tumor progression

Slide 74 · Selected textbook reading

Robbins, Cotran & Kumar: Pathologic Basis of Disease, 11th ed. (2026).

Neoplasia: Cancer-Enabling Inflammation; Evasion of Immune Surveillance; Invasion of Extracellular Matrix.

Inflammation and Repair: Macrophage Activation; Angiogenesis.